There have heretofore been known devices for controlling internal combustion engines based upon the pressure in the cylinders. Japanese Unexamined Patent Publication (Kokai) No. 9-53503 discloses a device of this kind for controlling internal combustion engines. In the device for controlling internal combustion engines disclosed in the above Japanese Unexamined Patent Publication (Kokai) No. 9-53503, the amount of fuel injection and the ignition timing are calculated based on an output value of a cylinder pressure sensor that detects the pressure in the cylinder.
When the pressure in the cylinder is detected by the cylinder pressure sensor as in the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-53503, however, the pressure in the cylinder that is detected is a peak combustion pressure at a moment of a crank angle of 10 to 15 degrees after the top dead center in the compression stroke. With the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-53503, therefore, it is not possible to control the internal combustion engines based on the pressure in the cylinder other than the peak combustion pressure in the cylinder, such as the pressue at the top dead center in the compression stroke. In addition, with the device for controlling internal combustion engines, which does not consider a change in the pressure in the cylinder accompanying a change in the opening areas of the intake and exhaust valves or a change in the working angle as a result of employing a variable valve mechanism as taught in Japanese Unexamined Patent Publication (Kokai) No. 9-53503, it is not possible to suitably control the internal combustion engine when the opening areas of the intake and exhaust valves vary or when the working angles thereof vary.
There has further been known a device for controlling internal combustion engines based on the temperature of a certain portion in the cylinder. The device for controlling internal combustion engines of this type has been disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 4-81574. In the device for controlling internal combustion engines taught in Japanese Unexamined Patent Publication (Kokai) No. 4-81574, the ignition timing is calculated based upon an output value of a wall temperature sensor that detects the temperature of the cylinder wall, and the internal combustion engine is controlled based on the thus calculated ignition timing.
In the device for controlling internal combustion engines taught in the above Japanese Unexamined Patent Publication (Kokai) No. 4-81574, the ignition timing is calculated based on the temperature of the cylinder wall, and the internal combustion engine is controlled based on the ignition timing. However, there is a considerable difference between the temperature of the cylinder wall and the temperature of gas in the cylinder. In addition, it can be said that a suitable ignition timing is determined based on the temperature of gas in the cylinder rather than the temperature of the cylinder wall. Therefore, the internal combustion engine cannot be suitably controlled by the device for controlling internal combustion engines, which calculates the ignition timing based on the temperature of the cylinder wall as taught in Japanese Unexamined Patent Publication (Kokai) No. 4-81574. Moreover, with the device for controlling internal combustion engines, which does not consider a change in the temperature of gas in the cylinder accompanying a change in the opening areas of the intake and exhaust valves or a change in the working angles thereof as a result of employing a variable valve mechanism taught in Japanese Unexamined Patent Publication (Kokai) No. 4-81574, it is not possible to suitably control the internal combustion engine when the opening areas of the intake and exhaust valves vary or when the working angles thereof vary. There has further been known a device for controlling internal combustion engines based upon the ratio or amount of an internal EGR gas by being provided with a variable valve mechanism for at least the intake valves or the exhaust valves. As a device for controlling internal combustion engines of this kind, there has been known the one disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 9-209895. The device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-209895 is equipped with a variable valve mechanism for shifting the opening/closing timing (valve timing) without varying the length of period for opening the intake valve, and calculates the ignition timing based on the sum of the amount of the internal EGR gas (recirculating amount of the internal exhaust gas) or the amount of the burnt gas taken into the cylinder again after blown back into the intake pipe and the amount of the burnt gas remaining in the cylinder, i.e. not exhausted from the cylinder, thereby to control the internal combustion engine based on the thus calculated ignition timing.
However, the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-209895 is not considering the amount of varying the opening areas of the intake and exhaust valves, though it is considering the amount of shifting the opening/closing timing of the intake and exhaust valves at the time of calculating the amount of the internal EGR gas. When the variable valve mechanism is provided with a function for varying the valve-lifting amount and when the opening areas of the intake and exhaust valves are varied by changing the valve-lifting amount, the real amount of the internal EGR gas varies to a considerable degree even though the opening/closing timings of the intake and exhaust valves are not shifted. When the amount of the internal EGR gas is calculated by the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-209895 without considering a change in the opening areas of the intake and exhaust valves despite the opening areas of the intake and exhaust valves are changing, therefore, the calculated amount of the internal EGR gas becomes considerably different from the real amount of the internal EGR gas. Namely, when the opening areas of the intake and exhaust valves are subject to change, the amount of the internal EGR gas is not correctly calculated by the device for controlling internal combustion engines taught in Japanese Unexamined Patent Publication (Kokai) No. 9-209895, which considers a change in the amount of the internal EGR gas accompanying a change in the opening areas of the intake and exhaust valves due, for example, to the variable valve mechanism. Accordingly, it is not possible to suitably control the internal combustion engines.
Further, the device for controlling the internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-209895 considers the amount of shifting the opening/closing timings of the intake and exhaust valves at the time of calculating the amount of the internal EGR gas but does not consider the amount of changing the rotational angle of the cam shafts that correspond to the periods of opening the intake and exhaust valves. On the other hand, when the variable valve mechanism is provided with a function for varying the working angles of the intake and exhaust valves, i.e., with a function for increasing or decreasing the periods for opening the intake and exhaust valves and when the working angles of the intake and exhaust valves are varied, the real amount of the internal EGR gas changes to a considerable degree even when the opening/closing timings of the intake and exhaust valves are not shifted, i.e., even when the peak timing of the valve-lifting amount is not changed. When the amount of the internal EGR gas is calculated by the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-209895 without considering a change in the working angles of the intake and exhaust valves though the working angles of the intake and exhaust valves are changing, therefore, the calculated amount of the internal EGR gas becomes considerably different from the real amount of the internal EGR gas. Namely, when the working angles of the intake and exhaust valves are subject to change, the amount of the internal EGR gas is not correctly calculated by the device for controlling internal combustion engines taught in Japanese Unexamined Patent Publication (Kokai) No. 9-209895, which does not consider a change in the amount of the internal EGR gas accompanying a change in the working angles of the intake and exhaust valves due, for example, to the variable valve mechanism. Accordingly, it is not possible to suitably control the internal combustion engines.
There has further been known a device for controlling internal combustion engines equipped with a variable valve mechanism for at least either the intake valves or the exhaust valves, based on a degree of turbulence in the cylinder that is estimated relying upon the opening area of the intake valve varied by the variable valve mechanism. A device for controlling internal combustion engines of this type has been disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 2000-73800. In the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-73800, it is estimated that the degree of turbulence in the cylinder decreases with a decrease in the opening area of the intake valve that is varied by the variable valve mechanism.
Namely, in the device for controlling internal combustion engines disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-73800, it is estimated that the degree of turbulence in the cylinder decreases with a decrease in the opening area of the intake valve that is varied by the variable valve mechanism. In practice, however, the degree of turbulence in the cylinder increases with a decrease in the opening area of the intake valve that is varied by the variable valve mechanism. Therefore, if it is estimated that the degree of turbulence in the cylinder decreases with a decrease in the opening area of the intake valve like in the device for controlling internal combustion engines as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-73800 and if the internal combustion engine is controlled based on the estimated degree of turbulence in the cylinder, then, the internal combustion engine is not suitably controlled when the opening area of the intake valve is varied by the variable valve mechanism.